1. Field of the Invention
This invention relates to a light splitter to be used in a light measuring apparatus or an information mark indicating apparatus in an optical device such as a camera or the like.
2. Description of the Prior Art
Various techniques of splitting part of an incident light beam by utilizing a minute concavo-convex structure on the surface of a planar plate are known. For example, FIG. 1 of the accompanying drawings shows the splitter disclosed in U.S. Pat. No. 3,521,542. In this splitter, an incident light beam L is reflected by minute incision structures 2a and 2b on a planar plate 1 provided near the focusing screen of a camera and is directed through an exit end surface to a photodetector, not shown. In this method, however, coating of silver or like material must be formed on the reflecting surfaces 3a and 3b of the incision structures 2a and 2b to provide highly reflective surfaces, and this leads to high cost. Also, in order that the light beam transmitted through the planar plate 1 may be utilized as the finder light beam for the purpose of focusing or composition decision, the reflecting surfaces 3a and 3b must be made very narrow, and it is technically very difficult to make only such minute surfaces into highly reflective evaporated surfaces.